Polyaxial bone screw with cam connection and lock and release insert

ABSTRACT

A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in a receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A retaining member for capturing the shank in the receiver includes a sloping surface for a frictional, press fit, cammed engagement with the shank. A compression insert having a resilient structure provides non-floppy positioning of the shank with respect to the receiver and also independent locking of the shank with respect to the receiver.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. Ser. No.61/395,692, filed May 14, 2010 and incorporated by reference herein.This application is also a continuation-in-part of U.S. patentapplication Ser. No. 12/009,130 filed Jan. 16, 2008 that claims thebenefit of U.S. Prov. Pat. App. Ser. No. 60/881,641 filed Jan. 22, 2007and is a continuation-in-part of U.S. patent application Ser. No.10/818,554, filed Apr. 5, 2004, now U.S. Pat. No. 7,662,175, which is acontinuation of U.S. patent application Ser. No. 10/464,633, filed Jun.18, 2003, now U.S. Pat. No. 6,716,214; and also U.S. patent applicationSer. No. 10/818,554 being a continuation-in-part of U.S. patentapplication Ser. No. 10/651,003, filed Aug. 28, 2003, all of thedisclosures of which are incorporated by reference herein. Thisapplication is also a continuation-in-part of U.S. patent applicationSer. No. 12/154,460 filed May 23, 2008 that claims the benefit of U.S.Prov. Pat. App. Ser. No. 60/931,362 filed May 23, 2007 and is acontinuation-in-part of U.S. patent application Ser. No. 11/140,343filed May 27, 2005, all of the disclosures of which are incorporated byreference herein. This application is a continuation-in-part of U.S.patent application Ser. No. 12/804,580 filed Jul. 23, 2010 that is acontinuation of U.S. patent application Ser. No. 11/522,503 filed Sep.14, 2006, now U.S. Pat. No. 7,766,915, that is a continuation-in-part ofU.S. patent application Ser. No. 11/024,543 filed Dec. 20, 2004, nowU.S. Pat. No. 7,204,838, all of the disclosures of which areincorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to polyaxial bone screws for use inbone surgery, particularly spinal surgery and particularly to suchscrews with compression or pressure inserts.

Bone screws are utilized in many types of spinal surgery in order tosecure various implants to vertebrae along the spinal column for thepurpose of stabilizing and/or adjusting spinal alignment. Although bothclosed-ended and open-ended bone screws are known, open-ended screws areparticularly well suited for connections to rods and connector arms,because such rods or arms do not need to be passed through a closedbore, but rather can be laid or urged into an open channel within areceiver or head of such a screw.

Typical open-ended bone screws include a threaded shank with a pair ofparallel projecting branches or arms which form a yoke with a U-shapedslot or channel to receive, a rod. Hooks and other types of connectors,as are used in spinal fixation techniques, may also include open endsfor receiving rods or portions of other structure.

A common mechanism for providing vertebral support is to implant bonescrews into certain bones which then in turn support a longitudinalstructure such as a rod, or are supported by such a rod. Bone screws ofthis type may have a fixed head or receiver relative to a shank thereof.In the fixed bone screws, the rod receiver head cannot be moved relativeto the shank and the rod must be favorably positioned in order for it tobe placed within the receiver head. This is sometimes very difficult orimpossible to do. Therefore, polyaxial bone screws are commonlypreferred.

Open-ended polyaxial bone screws allow rotation of the head or receiverabout the shank until a desired rotational position of the head isachieved relative to the shank. Thereafter, a rod or other longitudinalconnecting member can be inserted into the head or receiver andeventually the receiver is locked or fixed in a particular positionrelative to the shank. During the rod implantation process it isdesirable to utilize bone screws or other bone anchors that havecomponents that remain within the bone screw and further remain properlyaligned during what is sometimes a very lengthy, difficult procedure.

SUMMARY OF THE INVENTION

A bone anchor assembly according to the invention includes a shankhaving an upper portion or head and a body for fixation to a bone; areceiver defining an upper open channel, a cavity and a lower opening; acompression insert; and a retainer for capturing the shank upper portionin the receiver, the retainer being in press fit engagement with theshank upper portion, the upper portion and attached retainer beingpivotable with respect to the receiver prior to locking of the shankinto a desired configuration. The press-fit engagement between the shankupper portion and the retainer may also be described as a cam capture,with the retainer and/or shank upper portion having a sloping orinclined surface. The shank and retainer cooperate in such a manner thata partial rotation between the retainer and the shank brings the shankand retainer structures into locking engagement. The illustratedcompression insert operatively engages the shank upper portion and isspaced from the retainer. The compression insert frictionally engagesthe shank during assembly, providing non-floppy positioning of the shankwith respect to the receiver and also subsequent independent locking ofthe shank with respect to the receiver. The non-floppy temporaryfrictional holding is provided by at least one resilient surface on theinsert, compression of the resilient surface toward the insert duringthe temporary frictional holding is by an inner surface of the receiver.When the insert is pressed downwardly into locking engagement with theshank upper portion or head, the resilient surface returns to a neutralor near neutral position, resiliently pressing out against the receiverand locking the insert against the receiver. Thereafter, furthermanipulation of a rod or other longitudinal connecting member ispossible with the otherwise locked screw.

Objects of the invention include providing apparatus and methods thatare easy to use and especially adapted for the intended use thereof andwherein the tools are comparatively inexpensive to produce. Otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a polyaxial bone screwassembly according to the present invention including a shank, areceiver, a retainer and a compression insert and also shown with aclosure top and a longitudinal connecting member in the form of a rod.

FIG. 2 is an enlarged top plan view of the shank of FIG. 1.

FIG. 3 is an enlarged and partial front elevational view of the shank ofFIG. 1.

FIG. 4 is an enlarged and partial cross-sectional view taken along theline 4-4 of FIG. 2.

FIG. 5 is an enlarged and partial cross-sectional view taken along theline 5-5 of FIG. 2.

FIG. 6 is an enlarged top plan view of the receiver of FIG. 1.

FIG. 7 is an enlarged bottom plan view of the receiver of FIG. 1.

FIG. 8 an enlarged side elevational view of the receiver of FIG. 1.

FIG. 9 is an enlarged front elevational view of the receiver of FIG. 1.

FIG. 10 is an enlarged perspective view of the receiver of FIG. 1.

FIG. 11 is an enlarged cross-sectional view taken along the line 11-11of FIG. 8.

FIG. 12 is an enlarged cross-sectional view taken along the line 12-12of FIG. 9.

FIG. 13 is an enlarged cross-sectional view taken along the line 13-13of FIG. 8.

FIG. 14 is an enlarged perspective view of the retainer of FIG. 1.

FIG. 15 is an enlarged top plan view of the retainer of FIG. 1.

FIG. 16 is an enlarged bottom plan view of the retainer of FIG. 1.

FIG. 17 is an enlarged cross-sectional view taken along the line 17-17of FIG. 15.

FIG. 18 is an enlarged and partial front elevational view of the shankand retainer of FIG. 1 with portions broken away to show the detailthereof.

FIG. 19 is an enlarged top plan view of the insert of FIG. 1.

FIG. 20 is an enlarged bottom plan view of the insert of FIG. 1.

FIG. 21 is an enlarged perspective view of the insert of FIG. 1.

FIG. 22 is an enlarged side elevational view of the insert of FIG. 1.

FIG. 23 is an enlarged front elevational view of the insert of FIG. 1.

FIG. 24 is an enlarged cross-sectional view taken along the line 24-24of FIG. 23.

FIG. 25 is a front elevational view of the receiver and retainer of FIG.1 with portions broken away to show the detail thereof and furthershowing a stage of assembly of the retainer in phantom.

FIG. 26 is an enlarged and partial perspective view of the receiver,retainer and shank of FIG. 1 shown in an early stage of assembly.

FIG. 27 is an enlarged and partial front elevational view of thereceiver, retainer and shank of FIG. 1 shown in a stage of assemblysubsequent to that shown in FIG. 26, with portions broken away to showthe detail thereof and further showing cooperating portions of the shankand retainer in phantom.

FIG. 28 is an enlarged and partial front elevational view of thereceiver, retainer and shank of FIG. 1 shown in a stage of assemblysubsequent to that shown in FIG. 27, with portions broken away to showthe detail thereof and further showing cooperating portions of the shankand retainer in phantom.

FIG. 29 is a reduced front elevational view of the assembled receiver,retainer and shank of FIG. 28, showing a stage of assembly with theinsert of FIG. 1, shown in a side elevational loading position.

FIG. 30 is an enlarged cross-sectional view of the receiver, retainerand shank taken along the line 30-30 of FIG. 29 and further showing theinsert of FIG. 29 in top plan view, being shown in a stage of assemblywithin the receiver.

FIG. 31 is an enlarged cross-sectional view of the receiver, retainerand shank taken along the line 31-31 of FIG. 29 and further showing theinsert of FIG. 29 in cross-section in a first factory assembled positionwithin the receiver, and also showing in phantom the pair of receiverspring tabs being biased toward the insert.

FIG. 32 is a reduced side elevational view of the receiver, retainer,shank and insert of FIG. 31 with portions broken away to show the detailthereof.

FIG. 33 is a reduced side elevational view, with portions broken away,similar to FIG. 32, further showing the shank pivoted at an angle withrespect to the receiver.

FIG. 34 a is an enlarged and partial rear elevational view of theassembly of FIG. 32 with portions broken away to show the detailthereof, the insert being shown in the factory assembled position.

FIG. 34 b is an enlarged and partial rear elevational view of theassembly of FIG. 33 with portions broken away to show the detailthereof, the insert being shown in a subsequent second or lockedposition with respect to the receiver.

FIG. 35 is a top plan view of the assembly of FIG. 34, with portionsbroken away to show the detail thereof and further shown with the rod ofFIG. 1, the insert being pressable downwardly into the second or lockedposition by the rod.

FIG. 36 is an enlarged and partial side elevational view of the assemblyof FIG. 35, further showing the closure top of FIG. 1 in a stage ofassembly with the receiver with portions broken away to show the detailthereof.

FIG. 37 is an enlarged and partial side elevational view of the assemblyof FIG. 36 with portions broken away to show the detail thereof andshowing the closure top engaging the rod.

FIG. 38 is an enlarged and partial cross-sectional view taken along theline 38-38 of FIG. 37.

FIG. 39 is an enlarged and partial, partially exploded perspective viewof the assembled receiver, shank, retainer and insert of FIGS. 32-34further shown with an alternative deformable rod and an alternativeclosure top.

FIG. 40 is a partial side elevational view of the assembly of FIG. 39,shown fully assembled and with portions broken away to show the detailthereof.

FIG. 41 is an enlarged and partial cross-sectional view taken along theline 41-41 of FIG. 40.

FIG. 42 is a reduced and partial perspective view showing the assembledreceiver, shank, retainer and insert of FIGS. 32-34 with a cord, firstand second spacers located on either side of the receiver, a threadedconnecter, a rod and a closure top configured for slidable engagementwith the cord.

FIG. 43 is a perspective view of the cord and connector of FIG. 42 withportions broken away to show the detail thereof.

FIG. 44 is an enlarged and partial cross-sectional view taken along theline 44-44 of FIG. 42.

FIG. 45 is a reduced and partial, partially exploded view, showing theassembled receiver, shank, retainer and insert of FIGS. 32-34 with acord, a spacer and a closure top configured for fixed engagement withthe cord.

FIG. 46 is an enlarged and partial cross-sectional view, taken along theline 46-46 of FIG. 45 and showing the spacer and closure top in anassembled position.

FIG. 47 is an exploded perspective view of an alternative embodiment ofa polyaxial bone screw assembly according to the present inventionincluding a shank, a receiver, a retainer and a compression insert.

FIG. 48 is an enlarged perspective view of the receiver of FIG. 47.

FIG. 49 is an enlarged side elevational view of the receiver of FIG. 47.

FIG. 50 is an enlarged front elevational view of the receiver of FIG.47.

FIG. 51 is an enlarged cross-sectional view taken along the line 51-51of FIG. 50.

FIG. 52 is an enlarged cross-sectional view taken along the line 52-52of FIG. 49.

FIG. 53 is an enlarged perspective view of the insert of FIG. 47.

FIG. 54 is an enlarged side elevational view of the insert of FIG. 47.

FIG. 55 is an enlarged side elevational view of the insert of FIG. 47opposite to that shown in FIG. 54.

FIG. 56 is an enlarged front elevational view of the insert of FIG. 47.

FIG. 57 is a cross-sectional view taken along the line 57-57 of FIG. 56.

FIG. 58 is a cross-sectional view taken along the line 58-58 of FIG. 54.

FIG. 59 is an enlarged and partial front elevational view of theassembled receiver, retainer and shank of FIG. 47, shown in explodedview with the insert of FIG. 47, the insert being in a side elevationalloading position.

FIG. 60 is an enlarged top plan view of the assembled receiver, retainerand shank of FIG. 47, further showing the insert of FIG. 47 in top planview, being shown in a stage of assembly within the receiver.

FIG. 61 is an enlarged and partial perspective view of the assembledreceiver, retainer, shank and insert of FIG. 47 with a portion of thereceiver broken away to show the detail thereof.

FIG. 62 is a reduced and partial cross-sectional view taken along theline 62-62 of FIG. 61.

FIG. 63 is a partial cross-sectional view taken along the line 63-63 ofFIG. 62.

FIG. 64 is an enlarged and partial front elevational view of theassembly of FIG. 61, with portions broken away to show the detail of aninitial surface engagement between the insert and receiver.

FIG. 65 is an enlarged and partial perspective view of the assembly ofFIG. 47 shown assembled with a deformable rod and a closure top.

FIG. 66 is an enlarged and partial front elevational view of theassembly of FIG. 65 with portions broken away to show the detailthereof.

FIG. 67 is an enlarged and partial cross-sectional view taken along theline 67-67 of FIG. 65.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is also noted that any reference tothe words top, bottom, up and down, and the like, in this applicationrefers to the alignment shown in the various drawings, as well as thenormal connotations applied to such devices, and is not intended torestrict positioning of the bone attachment structures in actual use.

With reference to FIGS. 1-38 the reference number 1 generally representsa polyaxial bone screw apparatus or assembly according to the presentinvention. The assembly 1 includes a shank 4, that further includes abody 6 integral with an upwardly extending upper portion or capturestructure 8; a receiver 10; a retainer structure 12 and a compression orpressure insert 14. The shank 4, receiver 10, retainer 12 andcompression insert 14 are typically factory assembled prior toimplantation of the shank body 6 into a vertebra 13, as will bedescribed in greater detail below. FIG. 1 further shows a closurestructure 18 of the invention for capturing a longitudinal member, forexample, a rod 21 which in turn engages the compression insert 14 thatpresses against the shank upper portion 8 into fixed frictional contactwith the retainer 12, so as to capture, and fix the longitudinalconnecting member 21 within the receiver 10 and thus fix the member 21relative to the vertebra 13. The illustrated rod 21 is hard, stiff,non-elastic and cylindrical, having an outer cylindrical surface 22. Itis foreseen (and also will be described with respect to otherembodiments) that the rod 21 may be of a different stiffness, elastic,deformable and/or of a different cross-sectional geometry. The receiver10 and the shank 4 cooperate in such a manner that the receiver 10 andthe shank 4 can be secured at any of a plurality of angles,articulations or rotational alignments relative to one another andwithin a selected range of angles both from side to side and from frontto rear, to enable flexible or articulated engagement of the receiver 10with the shank 4 until both are locked or fixed relative to each othernear the end of an implantation procedure. The assembly isadvantageously configured and factory assembled to provide a surgeonwith a bone anchor exhibiting sufficient frictional engagement betweenthe compression insert and the shank upper portion that the shank ispositionable to a desired angle with respect to the receiver during andafter implantation if the shank and prior to locking of the polyaxialmechanism with the closure structure. In other words, the factorysupplied assembly includes a shank that is not floppy or loose withrespect to the receiver, allowing greater ease in handling andmanipulation during the surgical process. Locking of the insert onto theshank upper portion may also be performed prior to locking with theclosure top. Furthermore, inserts according to the invention areadvantageously configured to allow for a squeeze release to easilyprovide for repositioning of the angle of the bone screw shank, as willbe described in greater detail below.

The shank 4, best illustrated in FIGS. 1-5, is elongate, with the shankbody 6 having a helically wound bone implantable thread 24 (single ordual lead thread form) extending from near a neck 26 located adjacent tothe upper portion or capture structure 8, to a tip 28 of the body 6 andextending radially outwardly therefrom. During use, the body 6 utilizingthe thread 24 for gripping and advancement is implanted into thevertebra 13 leading with the tip 28 and driven down into the vertebrawith an installation or driving tool (not shown), so as to be implantedin the vertebra to near the neck 26, as more fully described in theparagraphs below. The shank 4 has an elongate axis of rotation generallyidentified by the reference letter A.

The neck 26 extends axially upward from the shank body 6. The neck 26may be of the same or is typically of a slightly reduced radius ascompared to an adjacent upper end or top 32 of the body 6 where thethread 24 terminates. Further extending axially and outwardly from theneck 26 is the shank upper portion 8 that provides a connective orcapture apparatus disposed at a distance from the upper end 32 and thusat a distance from the vertebra 13 when the body 6 is implanted in suchvertebra.

The shank upper portion 8 is configured for a pivotable connectionbetween the shank 4 (with attached retainer 12) and the receiver 10prior to fixing of the shank 4 in a desired position with respect to thereceiver 10. The shank upper portion 8 has an outer, convex andsubstantially spherical lower surface 34 that extends outwardly andupwardly from the neck 26 and terminates at a substantially planar ledgeor shelf 36 that is annular and disposed perpendicular to the shank axisA. The shelf 36 is sized and shaped to receive and seat the retainer 14at a bottom surface thereof as will be described in greater detailbelow. The spherical lower surface 34 has an outer radius that is thesame or substantially similar to an outer radius of the retainer 12 aswill be described in greater detail below, the surface 34 as well as theretainer 12 outer surface participating in the ball and socket jointformed by the shank 4 and attached retainer 12 within the partiallyspherical surface defining an inner cavity of the receiver 10. Extendingupwardly from the ledge 36 is a cylindrical surface 38, the surface 38having a radius that is smaller than the radius of the lower sphericalsurface 34. Extending substantially radially outwardly from thecylindrical surface 38 are three evenly spaced cam projections or lugs40, each with a lower surface or ledge 41 that faces toward the ledge 36and is disposed at a slight angle with respect thereto. As will bediscussed in greater detail below, the lower ledge 36, cylindricalsurface 38 and upper ledges 41 cooperate to capture and fix the retainer12 to the shank upper portion 8, prohibiting movement of the retainer 12along the axis A once the retainer 12 is located between the ledges 36and 41. It is noted that according to the invention, one, two, three ormore cam projections 40 may be disposed about the cylindrical surface38. Each of the projections 40 further include an outer substantiallycylindrical surface 42 bounded by opposed side surfaces 43. A partiallyspherical or domed top surface 44 partially defines each of theprojections 40, terminating at the projection surfaces 42 and thecylindrical surface 38 located between each of the cam projections 40.The spherical surface 44 has an outer radius configured for slidingcooperation and ultimate frictional mating with a substantiallyspherical concave surface of the compression insert 14 that has the sameor substantially similar radius as the surface 44. The radius of thesurface 44 is smaller than the radius of the lower spherical surface 34.Located near or adjacent to the surface 44 is an annular top surface 46.A counter sunk substantially planar base or seating surface 49 partiallydefines an internal drive feature or imprint 50. The illustratedinternal drive feature 50 is an aperture formed in the top surface 46and has a hex shape designed to receive a hex tool (not shown) of anAllen wrench type, into the aperture for rotating and driving the bonescrew shank 4. It is foreseen that such an internal tool engagementstructure may take a variety of tool-engaging forms and may include oneor more apertures of various shapes, such as a pair of spaced apartapertures or a multi-lobular or star-shaped aperture, such as those soldunder the trademark TORX, or the like. The seat or base 49 of the drivefeature 50 is disposed perpendicular to the axis A with the drivefeature 49 otherwise being coaxial with the axis A. In operation, adriving tool is received in the internal drive feature 50, being seatedat the base 49 and engaging the six faces of the drive feature 50 forboth driving and rotating the shank body 6 into the vertebra 13, eitherbefore the shank 4 is attached to the receiver 10 or after the shank 4is attached to the receiver 10, with the shank body 6 being driven intothe vertebra 13 with the driving tool extending into the receiver 10.

The shank 4 shown in the drawings is cannulated, having a small centralbore 51 extending an entire length of the shank 4 along the axis A. Thebore 50 is defined by an inner cylindrical wall of the shank 4 and has acircular opening at the shank tip 28 and an upper opening communicatingwith the internal drive 50 at the surface 49. The bore 51 is coaxialwith the threaded body 6 and the upper portion 8. The bore 51 provides apassage through the shank 4 interior for a length of wire (not shown)inserted into the vertebra 13 prior to the insertion of the shank body6, the wire providing a guide for insertion of the shank body 6 into thevertebra 13.

To provide a biologically active interface with the bone, the threadedshank body 6 may be coated, perforated, made porous or otherwisetreated. The treatment may include, but is not limited to a plasma spraycoating or other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

With particular reference to FIGS. 1 and 6-13, the receiver 10 has agenerally U-shaped appearance with a partially discontinuoussubstantially cylindrical inner and outer profiles. The receiver 10 hasan axis of rotation B that is shown in FIG. 1 as being aligned with andthe same as the axis of rotation A of the shank 4, such orientationbeing desirable, but not required during assembly of the receiver 10with the shank 4. After the receiver 10 is pivotally attached to theshank 4, either before or after the shank 4 is implanted in a vertebra13, the axis B is typically disposed at an angle with respect to theaxis A, as shown, for example, in FIG. 33.

The receiver 10 includes a partially cylindrical and partiallyfrusto-conical base 58 integral with a pair of opposed upstanding arms60A and 60B, the arms forming a cradle and defining a U-shaped channel62 between the arms 60A and B with an upper opening, generally 63, and aU-shaped lower seat 64, the channel 62 having a width for operablysnugly receiving the rod 21 between the arms 60A and B. Each of the arms60A and 60B has an interior surface, generally 66, that has acylindrical profile and further includes a partial helically wound guideand advancement structure 68 extending radially inwardly from thesurface 66 and located adjacent top surfaces 69 of each of the arms 60.In the illustrated embodiment, the guide and advancement structure 68 isa partial helically wound interlocking flangeform configured to mateunder rotation with a similar structure on the closure structure 18, asdescribed more fully below. However, it is foreseen that the guide andadvancement structure 68 could alternatively be a square-shaped thread,a buttress thread, a reverse angle thread or other thread-like ornon-thread-like helically wound discontinuous advancement structure foroperably guiding under rotation and advancing the closure structure 18downward between the arms 60, as well as eventual torquing when theclosure structure 18 abuts against the rod 21.

An opposed pair of tool receiving and engaging features, generally 71,are formed on outer surfaces 72 of the arms 60A and 60B. The illustratedfeatures 71 are in a T-shape form and include and upper groove or recess73 running substantially parallel to the respective top surface 69 thatdoes not extend through the respective arm 60A or 60B and a connectingtransverse, substantially rectangular lower recess or through bore 74that does extend from each arm outer surface 72 to each interior surface66, providing access to laterally extending spring tabs 75 that biasagainst the pressure insert 14 to prohibit reverse (illustrated ascounter-clockwise) rotational movement of the insert about the receiveraxis once the insert is loaded in the receiver 10, as will be describedin greater detail below. The aperture feature 71 and alternatively, anyadditional tool receiving and engaging apertures may be formed in thereceiver outer surfaces and used for holding the receiver 10 duringassembly with the shank 4, the retainer 12 and the insert 14, during theimplantation of the shank body 6 into a vertebra when the shank ispre-assembled with the receiver 10, and during assembly of the boneanchor assembly 1 with the rod 21 and the closure structure 18. It isforeseen that tool receiving grooves or apertures may be configured in avariety of shapes and sizes and be disposed at other locations on thereceiver arms 60A and 60B.

Returning to the interior surface 66 of the receiver arms 60A and 60B,located below the guide and advancement structure 68 on each of the armsis a discontinuous cylindrical surface 77, having a diameterapproximately the same as a greater diameter of the guide andadvancement structure 68. The space under the guide and advancementstructure 68 that is defined in part by the cylindrical surface 77 formsa run-out area for the closure top 18. With particular reference to FIG.11, on the arm 60A, the cylindrical surface 77 is adjacent to an uppersurface or ledge 76 that partially defines the flange form 68 run-outand also serves as an intermediate or temporary abutment feature (alongwith the cylindrical surface 77) for the insert 14 as shown, forexample, in FIG. 34 a, and as will be discussed in greater detail below.Adjacent to and located below the cylindrical surface 77 is adiscontinuous annular surface 78 that in turn is adjacent to adiscontinuous substantially cylindrical surface 80. The surface 80extends from the surface 78 to an annular lip or ledge 81 that isdisposed perpendicular to the axis B and extends radially inwardlytoward the axis B. On each arm 60A and 60B, a portion of the ledge 81 isadjacent to and integral with a sloping or curved transition surface 83that in turn is adjacent to and integral with an upper surface 84 of therespective spring tab 75. Adjacent to the annular lip 81 is anotherpartially discontinuous substantially cylindrical surface 86 thatpartially defines the arms 60A and 60B as well as extends into the base58. Thus the surface 86 also partially defines the lower seat 64 of theU-shaped channel 62. An inner surface 88 of the spring tab 75 isintegral with the surface 86. The surface 86 has a diameter smaller thanthe diameter of the cylindrical surface 80, but larger than the diameterof the surface 77; this diameter feature will come into play withrespect to the cooperation between the insert 14 and the receiver innersurfaces 76, 77, 78 and 86 as will be described in detail below. Asmentioned above, the surface 86 also partially defines an inner cavity,generally 90, of the base 58 of the receiver 10, the cavity 90 and theU-shaped channel 62 defining a through bore of the receiver 10 from thetop surface 69 to a bottom surface 92 thereof. Moving downwardly furtherinto the base cavity 90, a substantially conical surface 94 is adjacentto the cylindrical surface 86 and terminates at a radiused or sphericalseating surface 96. It is noted that the surface 94 as well as portionsof the surface 86 may be partially spherical or otherwise curved in someembodiments of the invention. The surface 96 is sized and shaped forslidably mating with the retainer structure 12 and ultimatelyfrictionally mating therewith as will be described in greater detailbelow. The spherical seating surface 96 is adjacent a flared surface oras shown, a series of beveled surfaces that provide a neck 97 that formsa bottom opening, generally 98, to the cavity 90 at the receiver bottomsurface 92. The neck 97 is sized and shaped to be smaller than an outerradial dimension of the retainer 12 when the retainer 12 is fixed to theshank upper portion 8, so as to form a restriction to prevent thestructure 12 and attached shank portion 8 from passing through thecavity 90 and out the lower exterior 92 of the receiver 10 duringoperation thereof.

Returning to the surface 86, with reference to FIGS. 12 and 13, and inparticular to the surface 86 that extends upwardly into the arms 60A and60B, formed within each of the substantially cylindrical surfaces 86 andlocated directly beneath the annular lip 81 is a recess, generally 100,partially defined by a rounded stop or abutment wall 102 and partiallydefined by a lower annular lip or ledge 103. As will be described ingreater detail below, the cooperating compression insert 14 includes acooperating structure 104 that extends outwardly from each arm thereofthat abuts against the respective abutment wall 102 of each of thereceiver arms, providing a centering stop or block when the insert 14 isrotated into place in a clockwise manner as will be described below.

Finally, returning to the laterally extending spring tabs 75, thatinclude top surfaces 84 and inner surfaces 88 previously describedherein, each spring tab 75 further includes a bottom surface 108 and anend surface 109. The surface 109 is adjacent to and extends between thesurfaces 108 and 84, the end surface 109 running substantially parallelto the receiver axis B. The end surfaces 109 of the opposing spring tabs75 generally face in opposite directions. As described more fully belowand shown, for example, in FIG. 31, during assembly, the tabs 75 arepressed radially inwardly to engage the insert 14 and prohibitcounter-clockwise motion of the insert 14 with respect to the receiver10.

With particular reference to FIGS. 1 and 14-18, the retainer 12 thatoperates to capture the shank upper portion 8 within the receiver 10 hasa central axis that is operationally the same as the axis A associatedwith the shank 4 when the shank upper portion 8 and the retainer 12 areinstalled within the receiver 10. The retainer 12 is typically made froma hard material, that also may be resilient, such as stainless steel ortitanium alloy, for embodiments (not shown) having a slit or slot thatwould allow for top or bottom loading, so that the retainer 12 may becontracted or expanded during assembly. The retainer structure 12 has acentral bore, generally 110, that passes entirely through the retainerstructure 12 from a top surface 112 to a bottom surface 114 thereof. Thebottom surface 114 is substantially planar and disposed perpendicular tothe axis A when the retainer is fixed to the shank 4 with the surface114 abutting the shank surface 36 as shown, for example, in FIG. 18. Thetop surface 112 is disposed at an angle with respect to the axis A whenthe retainer 12 is fixed to the shank 4, the surface 112 slopingradially downwardly to provide space and clearance between the retainer12 and the insert 14 when the assembly 1 is fully assembled and placedat any angle of inclination of the shank 4 with respect to the receiver10. A first inner cylindrical surface 116 defines a substantial portionof the bore 110. The cylindrical surface 116 is sized and shaped to beslidingly received about the cylindrical surface portion 38 of the shankupper portion 8. Extending inwardly radially from the surface 116 arethree evenly spaced cam projections or shelves 118 sized and shaped tocooperate with the cam projections 40 of the shank upper portion 8 forfixing the retainer 12 to the shank upper portion 8. The cam shelves 118extend from at or near the retainer bottom 114 to a location spaced fromthe retainer top 112. The cam shelves 118 are sized and shaped toprovide direct mating support with each shank projection 40. The camshelves 118 are also spaced from the top surface 112 to provide adequatespace for loading rotation and placement of the cam projections 40 ofthe shank upper portion 8 with respect to the retainer 12 duringassembly within the receiver 10 of the bone screw 1. Each of theillustrated cam shelves 118 includes an upper, sloping or slantedseating surface 120 and an opposed bottom surface 122 that is flush andintegral with the bottom surface 114 of the retainer 12. The illustratedcamming seating surfaces 120 are each disposed about midway between thetop 112 and the bottom 114 of the retainer 12, but may be locatedslightly higher or lower along the surface 116. Each camming shelf 118further includes opposed side surfaces 124 and 125 running from thebottom surface 114 to the seating surface 120. Each of the surfaces 124and 125 are curved and substantially concave. Each shelf includes aninner cylindrical surface 126 sized and shaped to slidingly mate withthe surfaces 42 of the cam projections 40 of the shank upper portion 8.The sloping seating surfaces 120 are sized to receive the lugs orprojections 40 at the surfaces 41 thereof, with the surfaces 36 and 41of the shank upper portion forming a cam track between which eachcamming shelf 118 slides and is captured and frictionally fixed. Adegree of inclination of the surface 120 substantially matches a degreeof inclination of the bottom surface 41 of the lug 40. In theillustrated embodiment, the degree of inclination is about threedegrees, but it is foreseen that it may be more or less than thatillustrated. In some embodiments according to the invention, one or boththe ramped surfaces 41 and 120 include a roughening, ridges or someother treatment to further aid frictional locking of the retainer 12with respect to each lug 40. Furthermore, in some embodiments of theinvention, fixing engagement between the lugs 40 and the shelves 122 maybe enhanced by a weld or adhesive. For example, the illustrated cammingshelves 118 are slightly wider than the shank projections 40 at the sidesurfaces 124 and 125 so as to advantageously accommodate a spot weld orother fixing or adhering structure or substance.

The retainer 12 also has a radially outer partially spherically shapedsurface 129 sized and shaped to mate with the partial spherical shapedseating surface 96 of the receiver 10. The surface 129 includes an outerradius that is larger than a radius of the lower opening 98 of thereceiver 10, thereby prohibiting the retainer 12 and the shank upperportion 8 from passing through the opening 98 once the retainer 12 isfixed to the shank upper portion 8 within the receiver cavity 90.Although not required, it is foreseen that the outer partiallyspherically shaped surface 129 may be a high friction surface such as aknurled surface or the like.

With particular reference to FIGS. 1 and 19-24, the compression orpressure insert 14 is illustrated that is sized and shaped to bereceived by and down-loaded into the receiver 10 through the channelopening 66 as illustrated in FIGS. 29-31. The compression insert 14 hasan operational central axis that is the same as the central axis B ofthe receiver 10. The compression insert 14 has a central channel orthrough bore, generally 130, substantially defined by an innersubstantially cylindrical surface 131 coaxial with an inner partiallyspherical surface 132. The compression insert 14 through bore is sizedand shaped to receive a driving tool (not shown) therethrough thatengages the shank drive feature 50 when the shank body 6 is driven intobone with the receiver 10 attached. The surface 132 is sized and shapedto slidingly receive and ultimately frictionally engage thesubstantially spherical or domed surface 44 of the shank upper portion 8such that the surface 44 initially frictionally slidingly and pivotallymates with the spherical surface 132 to create a ball-and-socket typejoint. The surfaces 44 and/or 132 may include a roughening or surfacefinish to aid in frictional contact between them once a desired angle ofarticulation of the shank 4 with respect to the receiver 10 is reached.

The compression insert 14 includes a substantially cylindrical base body134 integral with a pair of upstanding arms 135. The bore 130 isdisposed primarily within the base body 134 and communicates with agenerally U-shaped through channel 136 that is defined by the upstandingarms 135. The channel 136 has a lower seat 138 sized and shaped toclosely, snugly engage the rod 21. It is foreseen that an alternativeembodiment may be configured to include planar holding surfaces thatclosely hold a square or rectangular bar as well as hold a cylindricalrod-shaped or corded longitudinal connecting member. The arms 135disposed on either side of the channel 136 extend outwardly and upwardlyfrom the body 134. The arms 135 are sized and configured for ultimateplacement near the run-out below the receiver guide and advancementstructure 68. It is foreseen that in some embodiments of the invention,the arms may be extended and the closure top configured such the armsultimately directly engage the closure top for locking of the polyaxialmechanism. In the present embodiment, the arms 135 include top surfaces140 that are ultimately positioned in spaced relation with the closuretop 18, so that the closure top 18 frictionally engages and holds therod 21, pressing the rod 21 downwardly against the seating surface 138,the insert 14 in turn pressing against the domed top 44 of the shank 4to lock the polyaxial mechanism of the bone screw assembly 1. Theillustrated insert 14 further includes features that allow for anon-floppy frictional fit between the insert and the shank 4 duringassembly and also for a locking of the insert 14 with respect to theshank 4 prior to locking down of the closure top 18. These featuresinclude a key-hole like through slot 144 disposed within each arm 135running substantially vertically from the top surface 140 and throughthe base body 134. Furthermore, each arm 135 includes at least oneradially projected upper portion 146 with an outer partially cylindricalsurface 147 for engaging with the receiver 10 as will be described morefully below. It is foreseen that inserts 14 according to the inventionmay have at least one and up to a plurality of such portions 146. Theillustrated slots 144 open along opposed side surfaces 150 of the arms,the side surfaces 150 each also defining a portion of one of theprojected upper portions 146. Each slot 144 terminates at a cylindricalthrough bore 152 that also runs from the top surface 140 through thebase body 134 and out a base surface 153, the bore 152 being spaced frominner and outer surfaces of each of the arms 135. Each slot 144separates each arm 135 into an inner arm portion 154 and an outer armportion 155 that includes the respective projected upper portion 146,the portions 155 being compressible towards the portions 154 duringassembly of the insert 14 within the receiver 10 as will be described ingreater detail below. Each arm 135 further includes inner planar walls158 and inner sloping lower surfaces 159. Each outer arm portion 155further includes a generally vertically extending recess or partialaperture 160 sized and shaped to receive holding tabs 75, or, in someembodiments of the invention, crimped material from the receiver.

The pressure insert body 134 located between the arms 135 has an outerdiameter slightly smaller than a diameter between crests of the guideand advancement structure 68 of the receiver 10 allowing for top loadingof the compression insert 14 into the receiver opening 63, with the arms135 of the insert 14 being located between the receiver arms 60A and 60Bduring insertion of the insert 14 into the receiver 10. Once locatedbetween the guide and advancement structure above and the shank upperportion 8 below, the insert 14 is rotated into place about the receiveraxis until the arms 135 are directly below the guide and advancementstructure 68 as will be described in greater detail below. At some pointin the assembly, a tool (not shown) may be inserted into the receiverapertures, to press the tabs 75 into the insert recesses 160. It isnoted that assembly of the shank 4 with the retainer 12 within thereceiver 10, followed by insertion of the lower compression insert 14into the receiver 10 are assembly steps typically performed at thefactory, advantageously providing a surgeon with a polyaxial bone screwwith the lower insert 14 already held in alignment with the receiver 10and providing a non-floppy, but pivotable shank ready for insertion intoa vertebra. The compression or pressure insert 14 ultimately seatsexclusively on the surface 44 of the shank upper portion 8, with thebase surface 153 sloping upwardly and away from the shank upper portion8, providing clearance between the retainer 12 and the insert 14 duringpivoting of the shank 4 with respect to the receiver 10. The assemblymay be configured so that the insert 14 extends at least partially intothe receiver U-shaped channel 62.

With reference to FIGS. 1 and 35-38, the illustrated elongate rod orlongitudinal connecting member 21 can be any of a variety of implantsutilized in reconstructive spinal surgery, but is typically acylindrical, elongate structure having the outer substantially smooth,cylindrical surface 22 of uniform diameter. The rod 21 may be made froma variety of metals, metal alloys and deformable and less compressibleplastics, including, but not limited to rods made of elastomeric,polyetheretherketone (PEEK) and other types of materials.

Longitudinal connecting members for use with the assembly 1 may take avariety of shapes, including but not limited to rods or bars of oval,rectangular or other curved or polygonal cross-section. The shape of theinsert 14 may be modified so as to closely hold, and if desired, fix orslidingly capture the longitudinal connecting member to the assembly 1.Some embodiments of the assembly 1 may also be used with a tensionedcord. Such a cord may be made from a variety of materials, includingpolyester or other plastic fibers, strands or threads, such aspolyethylene-terephthalate. Furthermore, the longitudinal connector Maybe a component of a longer overall dynamic stabilization connectingmember, with cylindrical or bar-shaped portions sized and shaped forbeing received by the compression insert 14 of the receiver having aU-shaped channel (or rectangular- or other-shaped channel) for closelyreceiving the longitudinal connecting member. The longitudinalconnecting member may be integral or otherwise fixed to a bendable ordamping component that is sized and shaped to be located betweenadjacent pairs of bone screw assemblies 1, for example. A dampingcomponent or bumper may be attached to the longitudinal connectingmember at one or both sides of the bone screw assembly 1. A rod or bar(or rod or bar component) of a longitudinal connecting member may bemade of a variety of materials ranging from deformable plastics to hardmetals, depending upon the desired application. Thus, bars and rods ofthe invention may be made of materials including, but not limited tometal and metal alloys including but not limited to stainless steel,titanium, titanium alloys and cobalt chrome; or other suitablematerials, including plastic polymers such as polyetheretherketone(PEEK), ultra-high-molecular weight-polyethylene (UHMWP), polyurethanesand composites, including composites containing carbon fiber, natural orsynthetic elastomers such as polyisoprene (natural rubber), andsynthetic polymers, copolymers, and thermoplastic elastomers, forexample, polyurethane elastomers such as polycarbonate-urethaneelastomers.

With reference to FIGS. 1 and 36-38, the closure structure or closuretop 18 shown with the assembly 1 is rotatably received between thespaced arms 60A and 60B. It is noted that the closure 18 can be any of avariety of different types of closure structures for use in conjunctionwith the present invention with suitable mating structure on theupstanding arms 60A and 60B. It is also foreseen that the closure topcould be a twist-in or slide-in closure structure. The illustratedclosure structure 18 is substantially cylindrical and includes an outerhelically wound guide and advancement structure 162 in the form of aflange form that operably joins with the guide and advancement structure68 disposed on the arms 60A and 60B of the receiver 10. The flange formutilized in accordance with the present invention may take a variety offorms, including those described in Applicant's U.S. Pat. No. 6,726,689,which is incorporated herein by reference. It is also foreseen thataccording to the invention the closure structure guide and advancementstructure could alternatively be a buttress thread, a square thread, areverse angle thread or other thread like or non-thread like helicallywound advancement structure for operably guiding under rotation andadvancing the closure structure 18 downward between the arms 60A and 60Band having such a nature as to resist splaying of the arms when theclosure structure 18 is advanced into the U-shaped channel 62. Theillustrated closure structure 18 also includes a top surface 164 with aninternal drive 166 in the form of an aperture that is illustrated as astar-shaped internal drive such as that sold under the trademark TORX,or may be, for example, a hex drive, or other internal drives such asslotted, tri-wing, spanner, two or more apertures of various shapes, andthe like. A driving tool (not shown) sized and shaped for engagementwith the internal drive 166 is used for both rotatable engagement and,if needed, disengagement of the closure 18 from the receiver arms 60Aand 60B. It is also foreseen that the closure structure 18 mayalternatively include a break-off head designed to allow such a head tobreak from a base of the closure at a preselected torque, for example,70 to 140 inch pounds. Such a closure structure would also include abase having an internal drive to be used for closure removal. A base orbottom surface 168 of the closure is planar and further includes a point169 and a rim 170 for engagement and penetration into the surface 22 ofthe rod 21 in certain embodiments of the invention. The closure top 18may further include a cannulation through bore (not shown) extendingalong a central axis thereof and through the top and bottom surfacesthereof. Such a through bore provides a passage through the closure 18interior for a length of wire (not shown) inserted therein to provide aguide for insertion of the closure top into the receiver arms 60A and B.

Preferably, the shank 4, receiver 10, the retainer 12 and thecompression insert 14 are assembled at a factory setting that includestooling for holding and alignment of the component pieces andcompressing arm portions of the insert 14. Assembly of the shank 4, thereceiver 10, the retainer 12 and the compression insert 14 is shown inFIGS. 25-34 b. With particular reference to FIG. 25, the ring-likeretainer 12 is typically first inserted or top-loaded through theopening 63 with the top 112 and bottom 114 surfaces aligned with thereceiver axis B within the receiver U-shaped channel 62 and then intothe cavity 90 to dispose the structure 12 within the receiver base 58.Then, the retainer structure 12 is rotated approximately 90 degrees soas to be coaxial with the receiver 10 and then seated in slidingengagement with the seating surface 96 of the receiver 10. Withreference to FIGS. 26-28, the shank capture structure 8 is then insertedor bottom-loaded into the receiver 10 through the opening 98. Theretainer structure 12, now disposed in the receiver 10 is coaxiallyaligned with the shank capture structure 8 so that the camming lugs 40are received by the retainer 12 and moved between and through thecamming shelves 118 until the bottom surface 114 of the retainer 12engages the surface 36 of the shank upper portion 8. The retainer 12 isthen partially rotated about the axis A of the shank 4 until theretainer shelves 118 are received in the cam track formed by the shanksurface 36 and the shank projection camming or sloped surface 41. Withreference to FIGS. 27 and 28, as the retainer 12 is rotated, the shankprojection bottom surface 41 frictionally engages the ramped surface 120of the camming shelf 118, creating a press fit between the surfaces andfrictionally locking the retainer 12 between the lugs or projections 40and the shank upper portion 8 seat 36, the retainer 12 now in fixedcoaxial relationship with the shank 4. Preferably, the shank 4 and orthe retainer 12 are partially rotated to fully mate such structures at afactory setting that includes tooling for holding and precisely rotatingthe shank 4 and/or the retainer 12 until locking frictional engagementtherebetween is accomplished. Although not shown, it is noted that theretainer structure 12 may also have tooling features, such as a pair ofsmall apertures so that the retainer 12 is also securely held during therotation with respect to the shank 4. Permanent, rigid engagement of thecapture structure 8′ to the retainer structure 12 may be furthersupported by the use of adhesive, a spot weld, a deformation, or thelike. At this time both the shank 4 and the retainer 12 are in loose,rotatable and swivelable engagement with the receiver 10, while theshank upper portion 8 and the lower aperture or neck 97 of the receiver10 cooperate to maintain the shank body 6 in swivelable relation withthe receiver 10. Only the retainer 12 is in slidable engagement with thereceiver spherical seating surface 96. The shank upper end 44 and theshank body 6 are in spaced relation with the receiver 10. The shank body6 can be rotated through a substantial angular rotation relative to thereceiver 10, both from side to side and from front to rear so as tosubstantially provide a universal or ball joint.

With reference to FIGS. 29-34 b, the compression insert 14 is downloadedinto the receiver 10 through the upper opening 63 with the insert bottomsurface 153 facing the receiver arm top surfaces 69 and the insert arms135 located between the receiver arms 60A and 60B. The insert 14 islowered toward the channel seat 64 until the insert 14 is located belowthe surface run-out feature 76 of the guide and advancement structure 68and the spherical surface 132 engages the domed surface 44 of the shank4. Thereafter, the insert 14 is rotated in a clockwise manner asindicated by the arrow CL in FIG. 30 until the stop structures 104 ofthe insert 14 abut against the wall 102 of the recess stop 100 locatedon the receiver arms 60A and 60B (see FIG. 31). During such rotation,the upper projections 146 also engage the receiver cylindrical surface77, compressing the outer arm portions 155 toward the inner arm portions154 to provide a slidable friction fit between the insert 14 and thereceiver 10 at the surface 77. At this time, the insert 14 engages theshank upper portion 8 at the surface 44 in a manner that allows forpivoting of the shank with respect to the receiver 10 with effort, thusa frictional fit that advantageously allows for setting a desired angleof the shank 4 with respect to the receiver 10, that may be adjusted,but is not otherwise floppy or loosely movable. The surface 76 of thereceiver prohibits the insert 14 from moving upwardly away from theshank surface 44. With further reference to FIG. 31, at this time, thespring tabs 75 may be pressed inwardly into the insert recesses 160,preventing counter-clockwise movement of the insert 14 with respect tothe receiver 10. FIG. 34 a best illustrates the position of the insert14 with respect to the receiver 10 prior to implanting of the shank body6 into the vertebra 13.

With reference to FIG. 32, the assembly 1 made up of the assembled shank4, receiver 10, retainer 12 and compression insert 14 is screwed into abone, such as the vertebra 13, by rotation of the shank 4 using asuitable driving tool (not shown) that operably drives and rotates theshank body 6 by engagement thereof at the internal drive 50.Specifically, the vertebra 13 may be pre-drilled to minimize stressingthe bone and have a guide wire (not shown) inserted therein to provide aguide for the placement and angle of the shank 4 with respect to thevertebra. A further tap hole may be made using a tap with the guide wireas a guide. Then, the bone screw assembly is threaded onto the guidewire utilizing the cannulation bore 51 by first threading the wire intothe opening at the bottom 28 and then out of the top opening at thedrive feature 50. The shank 4 is then driven into the vertebra using thewire as a placement guide. It is foreseen that the shank and other bonescrew assembly parts, the rod 21 (also having a central lumen in someembodiments) and the closure top 18 (also with a central bore) can beinserted in a percutaneous or minimally invasive surgical manner,utilizing guide wires. At this time, the receiver 10 may be articulatedto a desired position with respect to the shank 4 as shown, for example,in FIG. 33.

With reference to FIGS. 34 a, 34 b and also FIG. 35, at this time, theinsert 14 may be placed into a fixed or locked position with respect tothe receiver 10 by pressing the insert 14 axially downwardly against theshank top surface 44. This may be done by pressing the rod 35 into theinsert 14 as shown in FIG. 35 or by tooling (not shown) that lowers theinsert 14 to a location out of engagement with the cylindrical surface77 as shown in FIG. 34 b. At such time, the outer arm portion 155resiliently moves or springs back toward a neutral position, and suchaction puts the outer arm portion 155 into a full, frictional engagementwith the lower receiver surface 86, locking the insert 14 against theshank upper portion 8, the shank 4 no longer movable with respect to thereceiver 10. At this time the surgeon may make other adjustments in therod 21 or other longitudinal connection assembly components withconfidence that the shank 4 and the receiver 10 of the assembly 1 isfully locked into a desired angular position. If, however, an adjustmentis desired, tools (not shown) may be inserted into the receiver aperture74 and the insert outer arm portion 155 may be compressed inwardlyradially toward the axis B, loosening the insert 14 from the receivercylindrical surface 86, and thus loosening engagement between the insertsurface 132 and the shank upper portion surface 44.

With reference to FIGS. 36-38, the rod 21 is eventually positioned in anopen or percutaneous manner in cooperation with the at least two bonescrew assemblies 1. The closure structure 18 is then inserted into andadvanced between the arms 60A and 60B of each of the receivers 10. Theclosure structure 18 is rotated, using a tool engaged with the innerdrive 166 until a selected pressure is reached at which point the rod 21engages the insert 14, biasing the insert spherical surface 132 againstthe shank spherical surface 44.

As the closure structure 18 rotates and moves downwardly into therespective receiver 10, the point 169 and rim 170 engage and penetratethe rod surface 22, the closure structure 18 pressing downwardly againstand biasing the rod 21 into engagement with the insert 14 that urges theshank upper portion 8 toward the retainer 12 and into locking engagementtherewith, the retainer 12 frictionally abutting the surface 96. Forexample, about 80 to about 120 inch pounds of torque on the closure topmay be applied for fixing the bone screw shank 6 with respect to thereceiver 10.

If removal of the rod 21 from any of the bone screw assemblies 1 isnecessary, or if it is desired to release the rod 21 at a particularlocation, disassembly is accomplished by using the driving tool (notshown) that mates with the internal drive 166 on the closure structure18 to rotate and remove such closure structure from the cooperatingreceiver 10. Disassembly is then accomplished in reverse order to theprocedure described previously herein for assembly.

With reference to FIGS. 39-41, the assembly 1 is illustrated with analternative rod 21′ and an alternative closure top 18′, thus theresulting assembly is identified as an assembly 1′. The rod 21′ issubstantially similar to the rod 21 in size and shape. However, the rod21′ is made from a deformable material, illustrated as a plasticmaterial. The closure top 18′ is substantially similar to the top 18with the exception that the top 18′ includes an outer annular flatbottom surface 168′ adjacent to an otherwise curved bottom that furtherincludes a central rounded point or projection 169′ located on aspherical or domed shape surface 170′. As best shown in FIG. 41, whenassembled, the closure top surface 168′ engages the insert arm topsurfaces 140, pressing the insert 14 in a downward direction toward theshank upper portion 8, providing locking of the insert 14 against theshank top surface 44 independent of any engagement between the closuretop 18′ and the rod 21′. The closure top surfaces 169′ and 170′ engageand penetrate the deformable rod 21′.

With reference to FIGS. 42-46, the assembly 1 of the invention is shownwith alternative closure tops 18″ and 18′″ as well as with a cord/cordcoupler combination 180 and a cord 182. With particular reference toFIGS. 42-44, he assembly 1″ is identical to the assembly 1 previouslydescribed herein with the exception of the rod 21 is replaced by thecord/cord coupler combination 180 and the closure 18 is replaced by theclosure 18″. The cord/cord coupler combination 180 further includes acord 184 with a lip 185 that is fixed within a coupler 187 that furtherincludes inner threads 189 for y attaching to a hard rod 190. Theillustrated assembly further includes spacers 192 and 193 that may becompressible or not. In operation, the cord 184 is placed in tension.The closure top 18″ includes a planar bottom surface 168″ sized andshaped to abut against the insert 14 top surface 140 as illustrated inFIG. 41 with respect to the assembly 1′, providing independent lockingof the shank 4 with respect to the receiver 10. Alternatively,sufficient locking of the bone screw 1″ may be provided by the insert 14outer arm portions pressing against the cylindrical surface 86 of thereceiver 10 as illustrated in FIG. 34 b with respect to the assembly 1.The bottom surface 168″ of the closure 18″ allows for the cord 180 toslide with respect to the receiver 10, the cord being fixed to the rod190 at the coupler 187. In such an arrangement, the cord 180 is alsofixed to another bone screw 1 (not shown) or fixed to a fixing orblocking structure (not shown) engaging the cord 184 at a locationopposite the spacer 193 or other cooperating bone screws.

With reference to FIGS. 45 and 46, the assembly 1″ is identical to theassembly 1 with the exception that the rod 21 is replaced by the cord182 and the closure 18 is replaced by the closure 18″. The closure 18′″includes a planar bottom rim 168″ as well as an extension or protrusion169′″ that engages and penetrates the cord 182, holding the cord 182 infixed engagement with the bone screw assembly 1″. Also illustrated is aspacer 194 that may be compressible or not. The cord 182 is preferablyin tension. For example, the assembly 1″ may be used in combination withthe assembly 1″ shown in FIGS. 42-44 with the spacer 193 located betweenthe bone screw assemblies 1″ and 1″, the cord 180 replacing the cord182. Thus, the cord 180 would be held in tension between the coupler 187and the bone screw closure 169′″.

With reference to FIGS. 47-63, an alternative embodiment of a boneanchor assembly according to the invention, generally 201 isillustrated. The assembly 201 includes a shank 204 having a shank body206 and an upper portion 208, a receiver 210, a cam retainer 212 and acompression or pressure insert 214. The assembly 201 is substantiallysimilar to the assembly 1 with the exception of certain features of thereceiver 210 and the insert 214 as will be described in detail below.Unlike the receiver 14, the receiver 214 includes a top surface, ratherthan an outer or side surface that frictionally engages the receiver 210to place the insert 214 into frictional engagement with the shank upperportion 208 prior to placement of a rod 21 or other longitudinalconnecting member into the receiver 210. Somewhat similar to the insert14, the insert 214 includes an outer surface that engages a cylindricalsurface of the receiver 210 to place the insert 214 into lockingengagement with the shank upper portion 208 prior to ultimate lockingwith a closure top (not shown) that may be the closure top 18, 18′, 18″or 18″ previously described herein with respect to the assemblies 1, 1′,1″ and 1″, the closure top chosen based upon the type of rod, cord orother longitudinal connecting member being placed within the receiver210. Similar to the insert 14, the insert 214 may be compressed orsqueezed to release locking engagement with the receiver 210 and theshank upper portion 208. The insert 214 advantageously provides such arelease-able locking engagement without the key hole slot feature of theinsert 14 as will be described in greater detail below.

With particular reference to FIGS. 47, 62 and 63, the shank 204 isidentical or substantially similar to the shank 4 of the assembly 1 andtherefore, among other things, includes a spherical surface 234, aretainer seat 236, three cam lugs or projections 240, a domed top 244,and an internal drive feature 250, the same or similar to the respectivespherical surface 34, retainer seat 36, cam lugs 40, domed top 44 andinternal drive 50 previously discussed herein with respect to the shank4. Similarly, the retainer 212 includes, among other things, a top 312,bottom 314, cam shelves 318 and outer spherical surface 329 that are thesame or substantially similar to the respective top 112, bottom 114, camshelves 118 and outer spherical surface 129 of the retainer 12previously described herein with respect to the assembly 1. The shank204 and the retainer 212 are assembled within the receiver 210 in amanner the same or substantially similar to that described previouslyherein with respect to the shank 4, retainer 12 and receiver 10 of theassembly 1.

Although substantially similar to the receiver 10, the receiver 210includes some features that are different than the receiver 10 and thusshall be described more fully herein. The receiver 210 includes a base258, arms 260A and 260B, a U-shaped channel 262, a channel upper opening263, channel lower seat 264, a guide and advancement structure 268, andarm top surfaces 269, that are the same or substantially similar to therespective base 58, arms 60A and 60B, U-shaped channel 62, channel upperopening 63, channel lower seat 64, guide and advancement structure 68,and arm top surfaces 69 previously described herein with respect to thereceiver 10. The receiver 210 further includes a T-shaped toolengagement feature 271 somewhat similar to the feature 71 of thereceiver 10. However, The feature 271 further includes a thin crimp wall275 that provides alignment for the insert 214 similar to the tabs 75 ofthe receiver 10. The crimp wall 275 is simply pressed inwardly radiallytoward the insert 214 to prohibit counter-clockwise rotation of theinsert 214 with respect to the receiver 210. Similar to the receiver 10,the receiver 210 includes a bottom abutment surface 276 of the guide andadvancement run-out located on the arm 260A, the surface 276frictionally engaging a top surface of the insert 214 as will bedescribed more fully below. Located beneath the surface 276 is adiscontinuous cylindrical surface 278 that communicates with anotherdiscontinuous cylindrical surface 280 having a diameter smaller than adiameter of the surface 278, the surface 280 cooperating with the insert214 to lock the insert against the shank upper portion 208 as will bedescribed more fully below. A receive cavity, generally 290 includes anupper cylindrical or slightly conical surface 294 and a sphericalseating surface 296 for sliding and ultimate frictional mating with theretainer spherical surface 329. The receiver 210 further includes alower neck 297 forming an opening 298 at a bottom surface 292 of thereceiver 210. Formed in the arm cylindrical surface 280 is a pocket orstop 300 for receiving a projection 304 of the insert 214 to prohibitclockwise movement of the insert 214 with respect to the receiver 210and thus provide alignment between the insert 214 and the receiver 210similar to what was previously described herein with respect to theinsert 14 and the receiver 10.

The insert 214 includes a bore, 330, an inner cylindrical surface 331,an inner spherical surface 332, a substantially cylindrical body 334,upstanding arms 335, a u-shaped channel 336, a channel seat 338 and armtop surfaces 340 substantially similar to the respective bore, 130,inner cylindrical surface 131, inner spherical surface 132,substantially cylindrical body 134, upstanding arms 135, u-shapedchannel 136, channel seat 138 and arm top surfaces 140 previouslydescribed herein with respect to the insert 14. However, the insert 214does not include the key-hole slot feature of the insert 214. Instead,at least one or both of the top surfaces 240 includes an upwardlysloping surface feature 342 spaced from a notch 343 formed in the insertarm 335. Thus, the notch 343 may be pressed downwardly toward the body334. FIG. 55 illustrates an embodiment wherein both surfaces 240 includethe surface feature 342, the second feature shown in phantom as 342′. Asbest illustrated in FIG. 62, the surface 342 engages the receiversurface 276 to hold the insert 214 against the shank upper surface 244after assembly therewith, so that a friction-fit, non-floppy engagementbetween the insert 214 and the shank top 208 allows for placement of theangle of the shank 204 with respect to the receiver 210 during surgeryand prior to the rod or other connecting member being placed in thereceiver 210. Furthermore, the arms 335 include upper portions 345 thatflare outwardly and are sized and shaped to cooperate with the surface280 of the receiver 210 (see FIG. 64) for tight frictional, locking fitbetween the insert 214 and the shank upper portion 208 when the insert214 is pushed downwardly toward the receiver base, either by a rod or bya tool. Such locking may be released by a inserting a tool (not shown)in the tool engagement feature 371 and pressing the insert 214 radiallyinwardly.

The insert 214 is loaded into the receiver 210 in a manner similar tothat described above with respect to the insert 14 and the receiver 10of the assembly 1. The assembly 201 is thereafter fitted with a rod 21or other longitudinal connecting member and a closure top 18 orcooperating top as described above with respect to the assembly 1.

With reference to FIGS. 65-67, the assembly 201 is shown with thedeformable rod 21′ and the closure top 18′ previously described herein.Thus, the resulting assembly is identified as 210′. As illustrated, theclosure 18′ presses and locks down upon the insert 214 at the surface340, independently locking the assembly 201 when the assembly is used tocapture the deformable rod 21′. Further independent locking is providedby the insert 214 pressing against the receiver surface 280.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

1. A medical implant comprising: a) a receiver having a lower portionwith a cavity and a lower opening communicating with the cavity and anupper portion with an upper opening communicating with a longitudinalconnecting member receiving channel, the channel communicating with thecavity; b) a bone screw shank having a head and a body for fixation tobone, the head having an engagement surface; c) a retaining member forcapturing the shank head within the receiver, the retaining memberhaving an interior surface sized and shaped for a locking press-fit,fixed engagement with the shank head engagement surface; and d) acompression insert positioned in the receiver and being in operativelocked engagement with the shank head.
 2. The implant of claim 1 whereinthe shank and retaining member cooperate in such a manner that a partialrotation between the retaining member and the shank brings the shank andretaining member into the locking press-fit engagement.
 3. The implantof claim 2 wherein the shank has a central axis and the partial rotationbetween the shank and retaining member is about the central axis.
 4. Theimplant of claim 1 wherein the shank head engagement surface is locatedon at least one outwardly extending projection, the projectionfrictionally mating with the retaining member interior surface.
 5. Theimplant of claim 4 wherein the at least one projection is a plurality ofprojections.
 6. The implant of claim 5 wherein the shank head has threeoutwardly extending projections.
 7. The implant of claim 1 wherein theshank head has a lower spherical surface having a radius and theretaining member has an outer spherical surface, a radius of the outerspherical surface being the same as the radius of the shank head lowerspherical surface, the outer spherical surface and the retaining memberlower spherical surface being adjacent.
 8. The implant of claim 7wherein the shank head lower spherical surface terminates at a shelf,the retaining member being seated on the shelf.
 9. The implant of claim8 wherein the shelf is a first shelf and the shank has at least oneprojection with a first inclined surface and the retaining member has asecond shelf with a second inclined surface, the first and secondinclined surfaces being in frictional engagement with a portion of theretaining member being located between the first shelf and the firstinclined surface.
 10. The implant of claim 1 wherein the compressioninsert has first and second positions with respect to the receiver, andwherein in the first position, the insert engages the upper portion ofthe receiver, the shank head being in movable frictional engagement withthe insert, and in the second position, the insert frictionally engaginga lower inner surface of the receiver with the insert being in lockedengagement with the shank head.
 11. The implant of claim 10 wherein theshank head has a top surface and the insert exclusively engages the topsurface and remains spaced from the retaining member in allarticulations of the shank with respect to the receiver.
 12. The implantof claim 1 wherein the receiver channel is a first channel and theinsert further comprises: a) a pair of opposed arms forming a secondchannel, the arms being substantially non-resilient, the second channelin alignment with the first channel; and b) at least one outer resilientstructure located near and slightly spaced from at least one of thearms, the resilient structure being compressible toward the at least onearm, the structure, when compressed, resiliently pressing against thereceiver during manipulation of the shank with respect to the receiverwith the shank head being in frictional, but movable engagement with theinsert.
 13. The implant of claim 12 wherein the resilient structure islocked against the receiver when the resilient structure is in a neutralto near neutral substantially non-compressed state and the insert isoperatively frictionally locked against the shank.
 14. The implant ofclaim 12 wherein the at least one outer compressible resilient structureand the at least one arm form a slit.
 15. The implant of claim 12wherein the at least one outer compressible resilient structure and theat least one arm form a through slit running from a top surface to alower surface of the insert.
 16. The implant of claim 12 wherein the atleast one outer compressible resilient structure is located at a topsurface of the insert.
 17. The implant of claim 12 having at least twocompressible resilient structures, one structure located at each arm.18. The implant of claim 1 wherein the receiver includes at least twoinner cylindrical walls of different diameters.
 19. A polyaxial bonescrew assembly comprising: a) a shank having a body for fixation to abone and an upper portion with a top surface, the upper portion havingan engagement structure, the upper portion further having a lowerpartial spherical surface having a first radius; b) a receiver definingan open channel and having a base with a seating surface partiallydefining a cavity, the open channel communicating with the cavity, thecavity communicating with an exterior of the base through an openingsized and shaped to receive the shank upper portion therethrough; c) aretainer for capturing the shank within the receiver, the retainer andthe shank engagement structure being sized and shaped for press fitlocking engagement therebetween, the retainer having an external partialspherical surface having a second radius, the retainer partial sphericalsurface and the shank lower partial spherical surface sized and shapedfor initial pivoting and ultimate fixed mating engagement with thereceiver seating surface, the first radius being substantially the sameas the second radius; and d) a compression insert positioned in thereceiver, the insert being in operative locked engagement with the shanktop surface.
 20. The assembly of claim 19 wherein the retainer has aninterior structure configured to engage and fix against the shankengagement structure, the shank and retainer cooperating in such amanner that a partial rotation between the retainer and the shank bringsthe shank and retainer structures into locking engagement.
 21. Theassembly of claim 20 wherein the shank has a central axis and thepartial rotation between the shank and retaining member is about thecentral axis.
 22. The assembly of claim 19 wherein the retainer is acontinuous closed ring.
 23. The assembly of claim 19 wherein the shankupper portion includes at least one lug for cammed engagement with theretainer.
 24. A bone anchor comprising: a) a receiver having a lowerportion with an inner seating surface partially defining a cavity and alower opening communicating with the cavity and an upper portion with anupper opening communicating with a longitudinal connecting memberreceiving channel, the channel communicating with the cavity; b) a boneattachment structure having a head with a top surface, a first planarsurface and a first partial spherical surface, the bone attachmentstructure also having a body for fixation to bone; c) a retaining memberhaving at least a second planar surface sized and shaped for press fitengagement with the first planar surface, the retaining member having asecond partial spherical surface, the first and second sphericalsurfaces having substantially the same radius, both the first and secondspherical surfaces receivable by the inner seating surface of thereceiver; and d) a compression insert positioned in the receiver andbeing in operative locked engagement with the head top surface.
 25. Thebone anchor of claim 24 wherein the bone attachment structure and theretaining member cooperate in such a manner that a partial rotationbetween the retaining member and the bone attachment structure resultsin a press fit engagement therebetween.
 26. The bone anchor of claim 25wherein the bone attachment structure has a central axis and the partialrotation between the bone attachment structure and the retaining memberis about the central axis.
 27. The bone anchor of claim 24 wherein thereceiver further comprises at least one spring tab resiliently pressingagainst the compression insert at an outer surface thereof, prohibitingrotation of the insert with respect to the receiver.
 28. The bone anchorof claim 24 wherein the compression insert has a resilient outer surfacesized and shaped to press against the receiver and temporarily hold theinsert in frictional engagement with the head top surface for non-floppypositioning of the bone attachment structure with respect to thereceiver.
 29. The bone anchor of claim 24 wherein the compression inserthas a resilient outer surface feature operatively frictionally lockingagainst an inner surface of the receiver partially defining the cavity.30. The bone anchor of claim 29 wherein the receiver inner surface is acylindrical surface.
 31. The retaining member of claim 24 being anintegral one-piece member.